Mechanism' of Abortion of Postfertilization Hybrid Embryo in Interspecific Backcross, Lycapersicon esculentum * (L. esculentum *L, peruvianum).

Abstract

The ovules 3-30 days after pollination (DAP) in the interspecific backcross, Lycopersicon esculentum×(L. esculentum×L. peruvianum) {E×(E×P)}, were observed to clarify the process of abortion of postfertilization hybrid embryo (APHE) by using nomarski differential interference contrast optics, and to estimate the optimum timing for the embryo rescue. The critical difference between E×E and E×(E×P) was that the hybrid embryo was usually accompanied with incompletely developed suspensor, remain of large polar nucleus or endosperm deterioration when compared with that of E×E at 7 DAP. About 90% of the hybrid embryos observed, however, continued to divide until the proliferated endothelium filled up the embryo sac cavity at 15 DAP (Fig. 4a, A type). On the other hand, the remains (about 10%) of the hybrid embryos developed in various types after 15 DAP. At 20 DAP, globular-stage embryo with incompletely developed suspensor (Fig. 4b, B type), and at 25 DAP, early globular-stage embryo with collapsed suspensor (Fig. 4c, C type) and a shrivelling embryo and suspensor (Fig. 4d, D type) were observed all in empty embryo sac cavity with different ratios, respectively (Table 1). These observations not only clarify the mechanism of APHE but also provide reliable information for efficient embryo rescue in interspecific hybridization in genus of Lycopersicon. Quantitative analysis of ovule growth in both E×E and E×(E×P) was also discussed.